In the prior art, numerous methods and apparatus have been proposed to produce a three-dimensional map or image of a distribution of radioactively tagged chemical substances. U.S. Pat. No. 4,833,327 to Hart discloses a high-resolution radioisotopic imaging system. The system accurately reconstructs using a high spatial resolution three-dimensional distributor of radioactivity of the kind encountered in lesion detection in nuclear medicine. A key feature of the invention is a plurality of electronic collimator detector elements arranged about a radioisotopic source field of radioisotopic atoms, each operating for simultaneously emitting a plurality of gamma-rays.
U.S. Pat. No. 5,005,195 to Lanza et al. discloses a method of determining bone mineral content, which is an indication of osteoporosis, using radiography. FIG. 3 thereof shows a detector module 14 capable of determining the optical intensity of radiation emitted by a radiation source and transmitted through a patient's limb. The patient's limbs are positioned between blocks, one block simulating bone and another block simulating tissue. A readout system for the detector is provided which includes a gating mechanism that receives signals simultaneously generated at a plurality of locations within the detector in response to a radiation event and an estimating mechanism for identifying the focus of the radiation event from the signals.
U.S. Pat. No. 4,611,247 to Ishida et al. discloses a radiation image reproducing apparatus that permits optical processed imagery to be reproduced. The image of an object is stored as a latent image from a recording medium such as a phosphorous sheet stimulated by radiation transmitted through the object. A reader exposes the recording medium to stimulating rays and photoelectrically reads the resulting light and enters the object's image onto an apparatus in the form of video signals. A processing unit is employed for processing various factors associated with images, such as gradation and spatial frequency.
U.S. Pat. No. 4,476,231 to Deindoerfer et al. discloses a method of analyzing a distribution of a reagent between particles and liquids in a suspension. The reagent may be labeled with a radioactive isotope which emits gamma-radiation. The apparatus includes a body containing a flow chamber having an examination area. A microscope is focused on the examination area, which is illuminated by a strobe light. The output of the microscope is focused on a CCD camera. The output from the CCD camera is converted to a series of still frame images. Electronic processors are used for evaluating these images and include a television monitor and frame grabber. The frame grabber stores the images of the subject used by the CCD.
U.S. Pat. Nos. 4,224,303 to Shaw, 3,876,882 to Todd, and 3,678,148 to Caiola disclose utilizing a radioactive material to track and/or analyze an analyte for medical or clinical investigation. In these patents, the radioactive particles are detected and displayed. In U.S. Pat. No. 4,224,303 to Shaw, the cumulative data from detection of the radioactive particles is produced into a three-dimensional representation of a lumen of a coronary arterial system.
The prior art also recognizes producing a three-dimensional image utilizing the combination of a microtome and scanning electron microscopy.
U.S. Pat. No. 4,377,958 to Leighton discloses a miniature microtome assembly in which the circuits of a sample section are optically observed by an operator's eye or by means of a camera. The disclosure of this patent is herein incorporated by reference for purposes of disclosing that which is well known in the art with respect to microtome apparatus.
The publication entitled "SEM Images of Block Faces, Cut by a Miniature Microtome Within the SEM--a Technical Note", Scanning Electron Microscopy II (1981), pages 73-76, by Leighton, discloses the use of a scanning electron microscope (SEM) to image successive surfaces of a sample section with a miniature microtome. This reference discusses the implications for a three-dimensional reconstruction of a sample as imaged by the scanning electron-microscope.
However, a need has developed in biological and other research to provide three-dimensional maps of the distribution of radioactively tagged chemical substances in order to determine the distribution of chemicals and other substances in a tissue or other matrix being studied. In response to this need, an apparatus and method have been developed for automatically and efficiently producing three-dimensional maps derived from the detection of radioactively tagged substances. The improved autoradiographic imaging method and apparatus include utilizing a charge coupled device in combination with a microtome to obtain a two-dimensional image of a body tissue sample. The microtome subsequently provides a series of tissue surfaces to be read by the charge coupled device to produce a series of two-dimensional views of the tissue sample. Image processing means produces a three-dimensional view from the series of two-dimensional images produced from the tissue samples.
As described above in U.S. Pat. No. 4,476,231 to Deindoerfer et al. and in U.S. Pat. No. 4,995,396 to Inaba et al., the prior art has proposed utilizing a CCD for detection of radioactivity. In the Inaba et al. patent, an imaging solid state imaging device, as, for example, a CCD, is used simultaneously as a radioactive ray detecting means. That is to say, when radioactive rays as gamma-rays enter the CCD, these radioactive rays will contact a PN-junction in the light-receiving part of the CCD and will issue a signal, the signal being translated to appear on a picture surface of a monitor as a bright point. Inaba et al. does not image but rather merely detects radiation. The radiation detection gives no information on the location of the radiation source other than the general direction in which the CCD as a whole is known to be pointing.
Although the prior art has proposed utilizing charge coupled devices or CCDs in conjunction with the detection of radioactive rays such as gamma-rays or the like, a need has developed for improved detection of biochemical or physiological parameters in the brains of humans and animals using real-time imagery. In response to this need, an improved in-vivo autoradiography method and apparatus has been developed which permits monitoring of these types of parameters over time while producing a two-dimensional image. A radioactively labeled substance is administered to a brain and changing patterns are continuously recorded using a charge coupled device.
In the field of electrophoresis, the prior art has also proposed imaging screens for detecting and storing information corresponding to a pattern of emission from an electrophoresis gel containing radioactively labeled substances. U.S. Pat. No. 5,028,793 to Lindmayer et al. discloses an imaging screen for electrophoresis applications and, more particularly, to an imaging screen for detecting and recording the impingement of beta-particles or visible light emitted from electrophoresis gels. In the patent to Lindmayer et al., an imaging screen is placed on an electrophoresis gel containing radioactively labeled protein fragments. The beta particles of the radioactive substances or visible light impinge upon the surface of the imaging screen. The light emitted from the imaging screen by release of trapped electrons is detected by a visual light detector such as a photomultiplier tube with mechanical scanning in two directions. A CID camera alternative uses a CID camera to sense light, not radiation, requires lenses and an infrared light source. The method and apparatus of Lindmayer et al. requires an imaging screen which includes a coating of an electron trapping material for releasably storing information corresponding to the flux in pattern of the emission from the radioactively labeled substance in the electrophoresis gel.
A need has developed to provide more accurate and automatic means to monitor the radioactive emissions of substances used in electrophoresis applications. In response to this need, an electrophoresis apparatus and method have been developed which utilizes a two-dimensional charge coupled device for use with an electrophoresis gel including radioactively tagged substances such as low-energy beta emitters. By this combination, very small sample volumes are attainable, and automatic end-point detection may be achieved, thereby optimizing runs.
None of the prior art cited above teaches or fairly suggests the concept of producing a three-dimensional image of a tissue sample utilizing the combination of a charge coupled device and a tissue sectionizing apparatus. In addition, the prior art does not teach or fairly suggest the utilization of a charge coupled device for use in real-time imaging of metabolic or physiological parameters in the brains of humans and animals or radioactive emissions in electrophoresis applications.